Porsche 930 Stuck in first

[Kent]

Hi,

I have an RCR P4, LS3 with 930. I was driving a couple weeks ago, shifting, and the car got stuck in first gear. Completely stuck. Nothing would pop it out of first. Also, It's not a clutch issue. I was far from home and got it towed, since I can only do 60 in 1st/ would overheat. It has RCR cable shift. If you go back to the trans, you can get a slight bit of movement on the shaft fore-aft, but it really doesn't want to twist. In opening the viewing window, I can't see anything broken, and I can probably figure out how to pop it out once I get the diagram, but I'm as much wondering why/how it could possibly get stuck in 1st in the first place if nothing broke? Is there something with the shift cables/ mechanism that could be out of adjustment? And if so, would this cause a 930 trans to get stuck in 1st? I don't want to get it unstuck just to have it get stuck again soon.

Thanks for any help you can provide.

 

[flatchat(Chris)]

Are the cables anywhere near exhausts ? the inner liner can melt and weld to the cable on cool down
Disconnect cable mechanisms at the gearbox and try moving the shifter shaft for gears -- if gears are selectable , then its the cable. If you can't get gears then we have a problem Houston

 

[Kent]

Ok, I had some time this evening in the garage. No issues with the cables. through the viewing window, it looks like the attached photo.

What you are looking at is the Top slot/rail (reverse). Then the middle rail/fork is 1st/2nd. And the bottom is 3rd/4th. So the fork for 1/2 actually rotated (along with the rail, not independent of it). downward to be between the 3 & 4 fork. Nothing is frozen, I can easily rotate it back up & out, and have all the gears again, but after putting everything back in-place and running through the gears a few times, the problem will recur and the car will be stuck in either 1st or 2nd.

I really know very little about transmissions, but I'm assuming that the 1 & 2 rail/ selector fork is not supposed to be able to rotate at all & It is only supposed to go fore/aft. Also, it rotates quite easily, I can do it with a finger. Is this an indication something is broken? Is it possible a bolt holding this rail in place & preventing it from rotating is just loose? Certainly seems like a strange problem to occur...

Thanks for any help!

 

[Jac Mac]

Sounds like the bolt that holds shifter fork for 1st,2nd has come loose or dropped out, pn's 24-23-13 in this drawing, not sure whether you can get this under an cover plug bolt on the case or not, been about 6 years since I was in a P-car box. Probably no one in Houston that can fix the problem....

 

[Kent]

Just an update. jac mac had it. The bolt for the 1/2 shift fork had just fallen-out completely. Pulled the rear and mid-case off, adjusted the 1/2 fork, put the bolt back in (with loc tite), and got it back together... Hard to see how it could have possibly come-out though unless the assembler had simply forgotten to torque it down.

Fourtunately it was all fairly easy to do in terms of access, didn't need to pull the trans.

 

[Jac Mac]

You got lucky, it could have ended up in two gears with a bit of power on given the 'right' circumstances.

 

[Scott]

Kent,
What kind of rpm are you running at 70 and 80mph with the 930? (I have a stock g50 and a stock 930 and am going to spend some money on gears soon) I run about 2800rpm at 80mph here in fl with the g50 and it is a little much for more than an hours drive... Thanks, Scott

P.S. Nice tube-frame rear clip support, that is one of my next mods!

 

[Bill Musarra]

Scott,
If he is running stock gears, 2000 will come up at 60 mph or there abouts(does with my 930 and 27+ inch tall rear tires). I am toying around with getting a taller gear if I don't buy a trailer. I think the trailer will work out best as it can be used for other things.

Bill

 

[Jack]

speed x 336 x final drive ratio / tire diameter = rpmtire diameter x rpm / 336 x final drive ratio = speed

the 336 is a constant

 

[Scott]

Bill,
I took a quick look around and didnt see any ring/pinions other than the stock 4.22/1 ratio. They do make a 3.10/1 for the g50 which is pretty good for us. At 3k plus the cost of tranny AND labor to change/repair anything once you get it open, seems like a new box is the ticket. Dunno, still looking at options! :O)

Thanks Jack. I was just looking for some user info. Scott

 

[Jac Mac]

I remembered that Russ Noble was in the process of changing the ratio's in his 930 before it all turned to bent metal-- post #584 in his build log - New ratios were going to be 1st 1.30/1, 2nd 1.04/1, 3rd 0.89/1, 4th 0.71/1 with speeds of 92,115, 134, 168. mph @ 6500 rpm. Hope his 'big' motor was capable of more RPM because that 6500 figure would leave him about 10/15 mph short on current results.
these ratio's which I suspect came out of a USA Fiero were going to 'fix' the big gap between 1st/2nd std 930 ratios.
Going to a taller R&P ratio would make the wide gap in std ratio's wider still.

 

[Dave]

What happened to Russ? I miss his and Lims posts?

 

[Scott]

Jac,
I do remember Russ's posts on that. The 930 is paired with a big block at the moment and will not take that kind of rpm at 80mph sustained. I also looked at changing fourth gear for freeway use, but with the standard r/p won't drop the rpm down far enough to make it livable. So, I may swap the g50 in with a r/p change/side-plate upgrade/cooler and cross my fingers! Otherwise it will be 10-14k for the RIGHT trans with correct ratios......... (

Oh well, gotta pay to play!! Scott

 

[Bill Musarra]

If I remember correctly, Russ changed his to get the ratios closer. The top end will suffer as a result. The gears he was using were a dog box setup, which are pretty loud and shifting has to be rather brisk(all the time). There are several charts of the gearing and speed on the Porsche web sites like these here.
930 transmission - Pelican Parts Technical BBS permalink #11.
The gears that are offered are posted in the different suplyers web sites. Here are the standard ratios.
930 TRANSAXLE SPECIFICATIONS-GBOX Transmission
And here are some of the different custom gears you can purchase at about $1500 apiece.
Retro Sport Online Store | Porsche All Parts | Porsche 930 Custom Gear Sets

There is an excellent discussion on 930 transaxel improvements on the forum which makes for good reading.
http://www.gt40s.com/forum/gt40-tech-powertrain-transaxles/35871-dg-930-porsche-930-transaxle-improvements.html

Bill

 

[Jac Mac]

What happened to Russ? I miss his and Lims posts?

Russ has got heavily involved in re-igniting the Formula Ford category in NZ motorsport scene, sponsoring & competing! Along with that he and domestic goddess were moving house slightly nth of Christchurch to a small livestock block ( was looking at a tractor to buy and had upgraded his Range Rover to one with most of the electrics functional! ).

Have not seen Lim for a few years, not his fault, more mine as Ive been putting some distance between me & motorsport of late. I see he still has a look on here occasionally & I suspect that he has made some progress on his GT40 endeavours.

Ross Nichol, that ex kiwi-ex Ozzie guy who used to supply us with entertaining race videos is now back in ChCh also on a lifestyle block IIRC, apparently with a Pantera to add to GT40 in garage, so he might spring up out of the woodwork to make a racing comeback once he & cars qualify for veteran class.
While the ChCh earthquakes were now some time ago, it will be some time yet before things get back to anything like normality for these guys & the people of ChCh, daily reminders of issues that have yet to be dealt with.

Back to OT & 930 stuff, IIRC Jack Ondrack purchased the parts inventory of a Porsche Transaxle guy in Canada a few years ago, might be worth contacting him to see if he has anything of use to you. Don't have his contact details, but you can probably find them in white pages for Alberta Canada.